Oxidation of hydroxylated aromatic compositions

ABSTRACT

Hydroxylated aromatic organic compositions are readily converted to the oxidized state by treatment with a mixture comprising a perchloro saturated aliphatic acid anhydride of from four to eight carbon atoms and an oxidizing agent selected from the class of metal nitrates or ammonium nitrate.

atent Crivello [451 July 18, 1972 OXIDATION OF HYDROXYLATED [56] References Cited AROMATIC COMPOSITIONS UNITED STATES PATENTS [72] Inventor: James V. Crlvello, Mechanicville, NY. 2,573,136 10/195 1 Gleim et al. ..260/396 Assigneez General El ic p y 2,657,222 l0/l953 Allen et al. ..260/396 [22] Filed: Oct. 23, 1969 Primary Examiner-Vivian Garner Attorney-Paul A. Frank, Charles T. Watts, William A. Teoli, Joseph T. Cohen, Frank L. Neuhauser, Oscar B. Waddell and [2]] Appl. No.: 868,919 Joseph B. Forman 52 us. Cl ..260/396 R, 260/378, 260/396 N, [571 ABSTRACT 2 /465 F, 260/4 7, 2 260/545 260/613 Hydroxylated aromatic organic compositions are readily con- 260/ 2 verted to the oxidized state by treatment with a mixture com- [5 Int. a pefchloro Saturated aliphatic acid anhydride of from of Search R, N, four to eight carbon atoms and an agent elected from the class of metal nitrates or ammonium nitrate.

10 Claims, No Drawings OXIDATION OF HYDROXYLATED AROMATIC COMPOSITIONS This invention is concerned with a process for oxidizing hydroxylated aromatic ring compositions. More particularly, the invention is concerned with a process for oxidizing compositions containing aromatic carbocyclic radicals having attached thereto a benzenoid hydroxyl radical, which process comprises treating such a hydroxylated aromatic composition (which term is intended to include polyhydroxylated compositions) with a mixture of ingredients comprising a perchloro saturated aliphatic acid anhydride of from four to eight carbon atoms and an oxidizing agent selected from the class consisting of metal nitrates and ammonium nitrate.

The oxidation of organic compositions, particularly the oxidation of aromatic compositions, is well known in the art and is an important industrial process for making many organic chemicals. As a result of the oxidation reaction, a wide variety of products is obtained depending on the compositions being oxidized, the oxidant, and the oxidation conditions. One of the more important oxidation reactions involves the oxidation of phenols and substituted phenols to quinones. A particularly important oxidation process is that involving the preparation of p-chloranil. p-Chloranil is a powerful oxidant and has been used in the oxidation and dehydrogenation of a large number of organic compounds.

I have now discovered that many of the difficulties associated with the prior oxidation of aromatic compounds, and particularly with respect to the preparation of the commercially attractive material, p-chloranil, e.g., undesirably large amounts of by-products and difiiculties associated with in the isolation of the desired reaction product, can be readily obviated by employing as the oxidation medium for the hydroxylated aromatic composition, a mixture of ingredients comprising a perchloro saturated aliphatic acid anhydride of from four to eight carbon atoms and an oxidant selected from the class consisting of metal nitrates and ammonium nitrate. Obviously mixtures of the anhydrides and of the oxidizing agents may be used without departing from the scope of the invention.

More particularly, l have found that by employing a mixture of the perchlorinated acid anhydride and the nitrate for the oxidation of hydroxylated aromatic compositions, greater yields under comparable conditions are obtained in many instances than has heretofore been possible, while at the same time realizing a reduction in the by-product yield of the reaction mixture. Moreover, the desired product can be readily isolated from the reaction mixture with a minimum of processing efiort. Additionally, the oxidants used in my process, namely, inorganic nitrates and ammonium nitrate, are relatively inexpensive and readily available in a high state of purity. Although the perchloroaliphatic acid anhydride may be consumed during the reaction and appears both as the chlorinated acid and as salts of the chlorinated acid, it can readily be regenerated by treating with fuming sulfuric acid to obtain again the perchlorinated aliphatic acid anhydride. Basically, my procedure is quite simple involving readily available starting materials and conventional equipment for making the desired oxidized products. Furthermore, the oxidizing agent (i.e., the nitrate) can be measured out precisely so that control over the reaction can be conveniently maintained. Finally, the yields of the desired products are quite good with little or no interference due to the presence of undesirable amounts of by-products.

The formation of oxidized products resulting from the reaction of the mixture of perchlorinated anhydride and the nitrate with the hydroxylated composition can lead to at least three different types of oxidation products. This result will generally depend on the presence or the type of group or groups nuclearly substituted on the aromatic ring in positions ortho or para to the hydroxyl group. Thus, it is possible to obtain diphenoquinones as a result of carbon-carbon coupling. In other instances, my oxidation reaction results in carbon-oxygen coupling.

The tendency towards carbon-carbon coupling usually occurs when the position on the aromatic nucleus immediately adjacent to the hydroxy group is occupied by a bulky substituent. In those instances, generally one obtains oxidized products comprising a diphenoquinone. For example, when the two ortho positions are blocked with bulky substituents, such as in the case of 2,6-di-t-butylphenol, carrying out the oxidation process described above results in carbon-carbon coupling exclusively, to give the corresponding 3,3',5,5'-tetrat-butyl diphenoquinone.

On the other hand, when less sterically hindered phenols are oxidized, for example, phenol itself, or in a specific instance, when a phenoxy phenol is employed, and there are no bulky sterically hindering groups adjacent the hydroxyl group, one obtains carbon-oxygen coupling. For instance, by subjecting phenol to oxidation in accordance with my claimed process, one would obtain phenoxy phenol.

The formation of products in the oxidation of specifically phenols may be explained by the following mechanism. In the first step, the inorganic nitrate reacts with v the perchloroaliphatic acid anhydride to generate a salt of the corresponding acid and also to form a perchloroaliphatic acid nitrate. Taking as an examplean inorganic nitrate identified as MNO (where M is a monovalent inorganic ion, e.g., sodium) and taking trichloroacetic anhydride as an example of a perchlorinated acid anhydride, the following steps generally are believed to take place:

(Cl CCO),O MNO Cl,,CC0-ONO Cl,CCOOM. Thereafter, reaction takes place between the phenol and the mixed anhydride to generate a phenol nitrate in accordance with the following equation where X is a t-butyl group Since aromatic nitrate esters are highly unstable, they undergo rapid reaction-to generate the phenoxy radical and a nitrogen dioxide radical in accordance with the following equation:

Two molecules ofthe iEt' ineins of a carbon-carbon coupling as shown by the following equation:

(not isolated) Under the same conditions, for instance, the dihydroxy diphenyl described above can be oxidized with the aforementioned trichloro acetyl nitrate to give the corresponding diphenoquinone having the formula Alternatively, when less sterically hindered phenols are oxidized, for instance, 2,6-dimethylphenol, the corresponding phenoxy phenol is formed being the product of carbon-oxygen coupling. These phenoxy phenols can further be treated under special oxidation conditions as, for instance, described in Kwiatek patent, U.S. Pat. No. 3,134,753 to give high molecular weight polymers.

In any event, it should be recognized that whatever the hydroxylated composition employed and regardless of the v kind of substitution, if any, adjacent the hydroxy] group on the aryl nucleus, there will be one form or another of oxidation reaction going on depending, as pointed out, on the presence or absence of bulky groups which will determine to a considerable extent whether a quinone structure will be formed, whether carbon-carbon coupling will occur, or whether carbon-oxygen coupling will occur. My oxidation process is intended to include all of these different types of oxidation reactions.

Among the perchloro saturated aliphatic acid anhydrides of from four to eight carbon atoms which may be employed in the practice of the present invention may be mentioned, for instance, trichloroacetic anhydride (identified as TCAA), pentachloro propionic acid anhydride, septachloro butyric acid anhydride, the mixed anhydride obtained from trichloroacetic acid and pentachloro propionic acid, etc.

The metallic nitrate (in addition to the ammonium nitrate) which is employed in the practice of the present invention advantageously has the general formula where M is a metal atom and the valences x and y of the metal and of the nitrate group can be varied depending upon the particular metal employed; accordingly, the number of nitrate groups in the metal nitrate will also be varied depending on the valence of the metal atom. Among such metal nitrates which may be employed may be mentioned, for instance, sodium nitrate, potassium nitrate, copper nitrate including the cupric and cuprous forms, cadmium nitrate, lead nitrate, silver nitrate, zirconium nitrate, chromium nitrate, etc. Various metal salts containing varying molecules of water of hydration are included within the term metal nitrate. It is preferred that the nitrate employed be either an alkali-metal nitrate such as sodium nitrate or ammonium nitrate because of their inexpense, ready availability, purity and the ability to readily isolate and remove from the reaction mixture, any salts derived from the nitrate.

The hydroxylated (non-polymeric) aromatic compounds which can be oxidized in accordance with the practice of the present invention are not critical and can be varied widely. Among the simple hydroxylated aromatic compositions (containing one or more nuclearly substituted hydroxy groups) which may be employed in the practice of the present invention may be mentioned, for instance, hydroxylated aromatic hydrocarbons (e.g., phenol, naphthol, anthrol, hydroxybiphenyl, hydroxyterphenyl, hydroquinone, etc.); aliphaticsubstituted aromatic hydrocarbons (e.g., p-cresol, m-cresol, 2,6-dimethylphenol, 2-ethylphenol, cavracrol, thymol, 4- butyl-2,6-dimethylphenol, B-methyl-a-naphthol, 2,6-dihexylphenol, 4,4-dihydroxy diphenyloxide, 2-hydroxystyrene, 4- allylphenol, ethylhydroquinone, etc.); halogenated hydroxylated aromatic compounds and halogenated aliphatic-sub stituted hydroxylated aromatic compounds (e.g., 4- chlorophenol, 2,6-dichlorophenol, 2,5-dichlorophenol, 2,3,5-

4 tribromophenol, 2,3,5,6-tetrachlorophenol, pentachlorophenol, 2,4,6-trifluorophenol, 2,3,6-triiodocresol,

2,3-dichloro-a-naphthol, 2,4-dichloro-3-methylphenol, dibromoanthrol, 3,3',5,5'-tetrachloro-4,4'-dihydroxy diphenylketone, etc.); aliphatic ethers of hydroxylated aromatic hydrocarbons, including alkyl derivatives (e.g., Z-methoxyphenol, 4-ethoxyphenol, 2-methoxy-B-methylphenol, 2,6- dimethoxyphenol, 2-allyloxyxylenol, etc.; aryloxy hydroxylated aromatic hydrocarbons (e.g., 4-hydroxydiphenyl ether, 4-phenoxy-a-naphthol, etc.); side chain and nuclearly halogenated aliphatic and aromatic ethers of aromatic hydrocarbons (e.g., 2',6-dichlorophenoxyphenol, 2,6,2',6- tetrachlorophenoxyphenol, 4-methoxy-3,S-dichlorophenol, 4- chloro-2-methoxyphenol, trichloromethoxyphenol, 2- chloromethylphenol, etc.); cyanohydroxylated aromatic compounds (e.g., Z-cyanophenol, B-cyanonaphthol, 2-cyano-6- chlorophenol, etc.); carboxy hydroxylated aromatic compounds (e.g., 2-carboxyphenol, 4-carboxy-3-methylphenol, 2,3,5,6-tetrachloro-4-carboxyphenol, etc.); polyhydroxylated aromatic compositions [e.g., hydroquinone, pyrogallol, resorcinol, bis(4-hydroxyphenyl)2,2-propane, tetrachlorohydroquinone, 3,3',5,5'-tetra-t-butyl-4,4'- biphenol, 4,4'-biphenol, etc.]; etc.

The ratio of the ingredients employed in my process can be varied widely. Thus, the molar ratio of the perchlorinated aliphatic acid anhydride to the metal nitrate or ammonium nitrate can be between about 25 to l and l to 25. The molar ratio of the ammonium nitrate or the metal nitrate to the hydroxylated aromatic compound can also be varied widely and advantageously is between about 15 to 1 and l to 15, while the molar ratio of the perchlorinated aliphatic acid anhydride to the hydroxylated aromatic compound is between about 25 to l and l to 50. Preferably, the molar ratio of the perchlorinated acid anhydride to the ammonium nitrate or the metal nitrate is between about 5 to l and l to 5; the molar ratio, the ammonium nitrate or metal nitrate to the hydroxylated aromatic compound is between about 3 to l and l to 8; and the molar ratio of the perchlorinated aliphatic acid anhydride to the hydroxylated aromatic compound is between about 1 to 3 and 10 to 1. Generally there should be present at least 1 mol of the anhydride per mol of the nitrate.

The temperature of the reaction can be also varied widely, but it has been found that temperatures between about l0 C. to about 50 C. or higher are adequate for the purpose. In determining the conditions of reaction, attention should be directed to the boiling points of the ingredients, and the possible necessity for pressure conditions, which can be employed if desired. Generally, ambient or room temperatures are suffcient thereby permitting operation of the process at temperatures ranging from about 20 to 35+ C. without the necessity for applying any heat. Since the reaction is somewhat exothermic, any additional heat which may be needed for accelerating the reaction can be derived from the exothermic conditions which will result. Generally temperatures above about C. should be avoided in order to avoid losses due to the formation of undesirable reaction products.

The reaction is advantageously camed out in a solvent which is inert to the reactants and to the reaction products. Included among such solvents may be mentioned aliphatic hydrocarbons, chlorinated aliphatic hydrocarbons and strongly deactivated aromatic compounds such as nitrobenzene, benzene sulfonic acid, etc. Specific compositions which may be employed for the purpose include chloroform, methylene chloride, acetonitrile, tetrachloroethane, hexane, ethylene dichloride, diethyl ether, dioxane, tetrahydrofuran, etc. If desired, the solvent can be the excess perchlorinated aliphatic acid anhydride over and above that necessary to give the desired oxidizing effect. The concentration of solvent is not critical and can be varied widely.

In carrying out the reaction, it is generally desirable to combine the inorganic nitrate with the hydroxylated aromatic composition, the perchlorinated aliphatic acid anhydride, and

the solvent and then to stir the reaction mixture for a period of from a few minutes to about 4 to 5 hours or more until the reaction is completed. The presence of a reflux condenser to take care of the more volatile products formed during the reaction is often desirable. Thereafter, the reaction products are recovered from the reaction mixture by usual means, such as removing the volatile reaction compositions and byproducts, such as solvent, N etc. Vacuum or slight heat to effect fractional distillation is often employed in this instance. Thereafter, the remaining mixture is advantageously mixed with water and the desired oxidized product may be removed by filtration or by extraction with a solvent in which the desired reaction product is soluble, depending on whether the product is a solid or liquid.

The oxidized compositions obtained in the practice of the present invention have many uses. Many of the oxidized products can be used as oxidants for other compositions, as dyestuffs, developers in photography, as monomers for making polymeric compositions, and as chemical indicators. Additionally the oxidized products (which contain the quinoid structure) can also be used as dehydrogenation agents.

In order that those skilled in the art can better understood how the present invention may be practiced, the following examples are given by way of illustration and not by way of limitation. All parts are by weight unless otherwise indicated. In the following examples, the percent yield found for the different reactions is calculated on the basis of the inorganic salt used and generally can be related to the following ratio:

EXAMPLE 1 Into a reaction vessel equipped with stirrer, thermometer, reflux condenser and drying tube were placed 2.47 grams (0.01 mol) tetrachlorohydroquinone, 0.8 gram (0.01 mol) ammonium nitrate, and 20 ml. CHCl To this mixture was added 5 ml. (0.028 mol) tn'chloracetic anhydride (TCAA), and the entire mixture was stirred for about 15 hours at ambient or room temperature (about 25-30 C.). At the end of this time, the reaction mixture was filtered to remove a precipitate which when washed with chloroform and then with water yielded 2.33 grams (95 percent yield) of p-chloranil, m.p. 290 C. The identity of the p-chloranil was established by the following analyses:

Found Theoretical C 29.4 29.3 Cl 561 57.72

EXAMPLE 2 In this example, employing the same equipment as in Example l, 2.06 grams (0.01 mol) 2,6-di-tertiary-butyl-phenol, 1.6 grams (0.02 mols) ammonium nitrate, 20 ml. acetone and ml. (0.055 mol) TCAA were mixed together for about three hours at ambient temperatures. At the end of this time, the precipitate which formed was removed by filtration, washed with distilled water, and dried to give pure, 3,3,5,5-tetra-tertiary-butyl-diphenoquinone in about a 30 percent yield and melting at 241 C.

EXAMPLE 3 Employing the equipment used in the preceding examples, 3.08 grams (0.02 mol) 2,6-dimethoxyphenol, 3.2 grams (0.04 mol) ammonium nitrate, and 50 ml. acetone were added to the reaction vessel and the mixture was stirred at around room temperature during which time 10 ml. (0.055 mol) TCAA was added. Immediate reaction ensued as evidenced by the fact that the purple diphenoquinone began to precipitate. After about three hours of stirring, the product was filtered and the solid precipitate was washed with acetone and then with water, dried in a vacuum oven, recrystallized from dimethylformamide to yield 2.44 grams yield) 3,3,5,5'- tetramethoxydiphenoquinone having a melting point of about 302 C. Analyses further established the identity of the quinone as evidenced by the following:

Calculated Found C 63.15 63.0 H 5.30 5.45 0 31.55 31.35

EXAMPLE 4 Employing the same equipment as in the previous examples, 13.3 grams (0.05 mol) pentachlorophenol, 4 grams (0.05 mol) ammonium nitrate, ml. CH CI, and 20 ml. (0.11 mol) TCAA were added to the reaction vessel. After about 15 hours of stirring, the solvent was removed and the remaining solid material placed in hot cyclohexane and filtered. 0n cooling the filtrate, 1.3 grams p-chloranil (m.p. 290 C.) was obtained.

EXAMPLE 5 When the procedure recited in Example 1 is repeated in all respects with the exception that the ammonium nitrate is replaced with 0.85 gram (0.01 mol) sodium nitrate, and 4.90 grams (0.01 mol) 3,3',5,5'4,4-biphenol is used in place of the hydroquinone, one obtains 3,3',5,5'-tetraphenyl diphenoquinone.

EXAMPLE 6 When CuSO -4H O is substituted for the ammonium nitrate of Example 1, good yields of p-chloranil are again obtained.

It will of course be apparent to those skilled in the art that other hydroxylated aromatic compounds can be oxidized in accordance with the present invention and the particular nitrate and perchloro aliphatic acid can be varied widely without departing from the scope of the invention. Additionally, the molar concentrations of the hydroxylated aromatic compound, the nitrate, and the perchlorinated aliphatic acid anhydride can be varied widely and are not critical as long as there is present a sufficient amount of the perchlorinated aliphatic acid anhydride to react with the inorganic nitrate to form the perchloro aliphatic acid nitrate which is required for oxidation purposes.

What I claim as new and desired to secure by Letters Patent of the United States is:

l. The process for oxidizing a hydroxylated aromatic compound selected from the class consisting of mono and poly hydroxylated hydrocarbon phenols and nuclear substituted mono and poly hydroxylated hydrocarbon phenols wherein the substituents are selected from the group consisting of halogen, lower alkyl, allyl, lower alkoxy, halogenated lower alkoxy, phenoxy, halogenated phenoxy, carboxy and cyano, which process comprises treating the said compound with a mixture of a perchloro saturated aliphatic acid anhydride of from four to eight carbon atoms and a nitrate selected from the class consisting of sodium nitrate, potassium nitrate, copper nitrate, cadmium nitrate, lead nitrate, silver nitrate, zirconium nitrate, chromium nitrate and ammonium nitrate.

2. The process as in claim 1 wherein the perchloro saturated aliphatic acid anhydride is trichloroacetic anhydride.

3. The process as in claim 1 wherein the hydroxylated aromatic compound is 2,6,-dimethoxy phenol.

4. The process as in claim 1 wherein the nitrate is copper nitrate.

5. The process as in claim 1 wherein the hydroxylated aromatic compound is pentachlorophenol.

6. The process as in claim 1 wherein the hydroxylated aromatic compound is 2,6-di-t-butylphenol.

7. The process for making chloranil which comprises treating 2,3,5,6-tetrachlorohydroquinone with a mixture of a perchloro saturated aliphatic acid anhydride of from four to 9. The process as in claim 7 wherein the nitrate is ammonium nitrate.

10. The process as in claim 7 wherein the perchloro saturated aliphatic acid anhydride is trichloroacetic anhydride and the nitrate is ammonium nitrate.

l I i I i 

2. The process as in claim 1 wherein the perchloro saturated aliphatic acid anhydride is trichloroacetic anhydride.
 3. The process as in claim 1 wherein the hydroxylated aromatic compound is 2,6,-dimethoxy phenol.
 4. The process as in claim 1 wherein the nitrate is copper nitrate.
 5. The process as in claim 1 wherein the hydroxylated aromatic compound is pentachlorophenol.
 6. The process as in claim 1 wherein the hydroxylated aromatic compound is 2,6-di-t-butylphenol.
 7. The process for making chloranil which comprises treating 2, 3,5,6-tetrachlorohydroquinone with a mixture of a perchloro saturated aliphatic acid anhydride of from four to eight carbon atoms and a nitrate selected from the class consisting of ammonium nitrate, sodium nitrate, potassium nitrate, copper nitrate, cadmium nitrate, lead nitrate, silver nitrate, zirconium nitrate, and chromium nitrate.
 8. The process as in claim 7 wherein the perchloro saturated aliphatic acid anhydride is trichloroacetic anhydride.
 9. The process as in claim 7 wherein the nitrate is ammonium nitrate.
 10. The process as in claim 7 wherein the perchloro saturated aliphatic acid anhydride is trichloroacetic anhydride and the nitrate is ammonium nitrate. 